| Message ID | 20190516055422.16939-1-vaibhav@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | dax: Fix last_page check in __bdev_dax_supported() | expand |
On Wed, May 15, 2019 at 10:55 PM Vaibhav Jain <vaibhav@linux.ibm.com> wrote: > > Presently __bdev_dax_supported() checks if first sector of last > page ( last_page ) on the block device is aligned to page > boundary. However the code to compute 'last_page' assumes that there > are 8 sectors/page assuming a 4K page-size. > > This assumption breaks on architectures which use a different page > size specifically PPC64 where page-size == 64K. Hence a warning is > seen while trying to mount a xfs/ext4 file-system with dax enabled: > > $ sudo mount -o dax /dev/pmem0 /mnt/pmem > XFS (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk > XFS (pmem0): DAX unsupported by block device. Turning off DAX. > > The patch fixes this issue by updating calculation of 'last_var' to > take into account number-of-sectors/page instead of assuming it to be > '8'. Yes, I noticed this too and fixed it up in a wider change that also allows device-mapper to validate each component device. Does this patch work for you? https://lore.kernel.org/lkml/155789172402.748145.11853718580748830476.stgit@dwillia2-desk3.amr.corp.intel.com/
Dan Williams <dan.j.williams@intel.com> writes: > On Wed, May 15, 2019 at 10:55 PM Vaibhav Jain <vaibhav@linux.ibm.com> wrote: >> >> Presently __bdev_dax_supported() checks if first sector of last >> page ( last_page ) on the block device is aligned to page >> boundary. However the code to compute 'last_page' assumes that there >> are 8 sectors/page assuming a 4K page-size. >> >> This assumption breaks on architectures which use a different page >> size specifically PPC64 where page-size == 64K. Hence a warning is >> seen while trying to mount a xfs/ext4 file-system with dax enabled: >> >> $ sudo mount -o dax /dev/pmem0 /mnt/pmem >> XFS (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk >> XFS (pmem0): DAX unsupported by block device. Turning off DAX. >> >> The patch fixes this issue by updating calculation of 'last_var' to >> take into account number-of-sectors/page instead of assuming it to be >> '8'. > > Yes, I noticed this too and fixed it up in a wider change that also > allows device-mapper to validate each component device. Does this > patch work for you? > > https://lore.kernel.org/lkml/155789172402.748145.11853718580748830476.stgit@dwillia2-desk3.amr.corp.intel.com/ Thanks Dan, I tested your patch and not seeing the issue anymore. So, please ignore this patch.
On Thu, May 16, 2019 at 10:37 PM Vaibhav Jain <vaibhav@linux.ibm.com> wrote: > > Dan Williams <dan.j.williams@intel.com> writes: > > > On Wed, May 15, 2019 at 10:55 PM Vaibhav Jain <vaibhav@linux.ibm.com> wrote: > >> > >> Presently __bdev_dax_supported() checks if first sector of last > >> page ( last_page ) on the block device is aligned to page > >> boundary. However the code to compute 'last_page' assumes that there > >> are 8 sectors/page assuming a 4K page-size. > >> > >> This assumption breaks on architectures which use a different page > >> size specifically PPC64 where page-size == 64K. Hence a warning is > >> seen while trying to mount a xfs/ext4 file-system with dax enabled: > >> > >> $ sudo mount -o dax /dev/pmem0 /mnt/pmem > >> XFS (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk > >> XFS (pmem0): DAX unsupported by block device. Turning off DAX. > >> > >> The patch fixes this issue by updating calculation of 'last_var' to > >> take into account number-of-sectors/page instead of assuming it to be > >> '8'. > > > > Yes, I noticed this too and fixed it up in a wider change that also > > allows device-mapper to validate each component device. Does this > > patch work for you? > > > > https://lore.kernel.org/lkml/155789172402.748145.11853718580748830476.stgit@dwillia2-desk3.amr.corp.intel.com/ > > Thanks Dan, I tested your patch and not seeing the issue anymore. Thanks, I recorded a "Tested-by" for you.
diff --git a/drivers/dax/super.c b/drivers/dax/super.c index bbd57ca0634a..6b50ed3673d3 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -116,7 +116,9 @@ bool __bdev_dax_supported(struct block_device *bdev, int blocksize) return false; } - last_page = PFN_DOWN(i_size_read(bdev->bd_inode) - 1) * 8; + /* Calculate the first sector of last page on the block device */ + last_page = PFN_DOWN(i_size_read(bdev->bd_inode) - 1) * + (PAGE_SIZE >> SECTOR_SHIFT); err = bdev_dax_pgoff(bdev, last_page, PAGE_SIZE, &pgoff_end); if (err) { pr_debug("%s: error: unaligned partition for dax\n",
Presently __bdev_dax_supported() checks if first sector of last page ( last_page ) on the block device is aligned to page boundary. However the code to compute 'last_page' assumes that there are 8 sectors/page assuming a 4K page-size. This assumption breaks on architectures which use a different page size specifically PPC64 where page-size == 64K. Hence a warning is seen while trying to mount a xfs/ext4 file-system with dax enabled: $ sudo mount -o dax /dev/pmem0 /mnt/pmem XFS (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your own risk XFS (pmem0): DAX unsupported by block device. Turning off DAX. The patch fixes this issue by updating calculation of 'last_var' to take into account number-of-sectors/page instead of assuming it to be '8'. Fixes: ad428cdb525a ("dax: Check the end of the block-device capacity with dax_direct_access()") Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com> Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com> --- drivers/dax/super.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)